Three paths still resolved the raw model/remote-supplied string before the
guard could refuse it, so on Windows the NTLM-leak trigger (resolving the
path) ran anyway: the file-checkpoint helper stats write_file/patch targets
before the tool executes; the ACP file bridge resolves fs/read_text_file and
fs/write_text_file paths before its read/write denylists; and @file:/@folder:
references resolve their target before the reference allow-check. Each now
checks the raw string first and refuses. The GLOBALROOT form now requires
its path separator so a GLOBALROOT-prefixed local name is not misclassified.
The rationale comment names the vector instead of another product's
changelog, and the security docs say the row is enforced on reads as well
as writes, since it sits under the write-guard table.
search_tool resolved its root via _resolve_path_for_task BEFORE the
NT-namespace check saw it (review finding): on Windows the resolve is the
SMB-auth trigger, on POSIX the task-base join hides the prefix from the
resolved-path denylist. The raw-string guard now runs first there too,
and the guard rides the existing top-level agent.file_safety import
instead of two function-local imports.
The tool-layer chokepoint test now covers all four entries and proves
none of them touched Path/_resolve_path_for_task/realpath before the
refusal; the 12 form-matrix tests collapse into one blocked/allowed
invariant over both classifiers.
Claude Code v2.1.234 (Aug 17, 2026) hardened its pre-approval file
accesses to reject Windows NT-namespace (\??\) paths against the NTLM
credential-leak vector. Port the same guard into Hermes file safety:
- agent/file_safety.py: is_nt_namespace_path() / get_nt_namespace_error()
raw-string check (never resolves — resolving IS the leak trigger).
Wired as the first check in get_read_block_error() and the write
denial classifier.
- tools/file_tools.py: raw-string guard at read_file_tool entry and in
_check_sensitive_path (covers write_file_tool + patch_tool), before
the task-base join can anchor the prefix under a POSIX base dir.
- Blocks \??\, \\.\, \\?\UNC\, \\?\GLOBALROOT. Extended-length
local drive paths (\\?\C:\...) and plain UNC shares stay allowed.
- tests/agent/test_nt_namespace_guard.py: 10 blocked forms, 11 allowed
forms, no-resolve proof, tool-layer chokepoint coverage.
- docs: protected-paths table in user-guide/security.md
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